Netiquette is the informal code of conduct that governs what is generally considered to be the acceptable way for users to interact with one and other online.

Here are some basic guidelines.

The Internet is a public forum.
Remember that anything you type or say in a chat session or post to a newsgroup is a public comment.

Abbreviations are welcomed.
There are many short forms for common words or phrases.
BTW means "by the way"
*g* or <G> indicates grinning
IMHO means "in my humble opinion"
ROTFL means "rolling on the floor laughing"
TTYL means "talk to you later"

Avoid using capital letters.
Capital letters symbolize shouting. Nobody likes to be yelled at.

Keep your communications brief.
Many people pay for Internet access by the hour. The longer it takes them to read your message, the more it cost them.

Personalizing your message.
Emoticon, also known as Smileys, are used as an expression of feelings.
Here are some examples:
: ) typical smiley
B) smiley wearing sunglasses
=D very happy smile